Firstly, fry the onions, garlic and ginger in a little vegetable oil for a few minutes, then add the courgettes and pepper. Cook the vegetables for about 4 minutes, then pour in the coconut milk and all the other ingredients apart from the prawns. Cook the dish for roughly 15 minutes, and add the prawns when you are nearly ready to serve. They should take a few minutes to go pink. Serve with boiled rice, and garnish with fresh coriander.